Association Between Retinal Layer Thickness and Cognitive Decline in Older Adults
Published on MedED: 11 June 2022
Type of article: Clinical Trial Summary
MedED Catalogue Reference: MOT006
Compiler: Linda Ravenhill
SourcesL JAMA Ophthalmology
Early diagnosis of Alzheimer's is key to implementing effective treatment and management strategies.
Much attention, therefore, has been focused on identifying biomarkers to assist in the diagnostic process, such as cerebrospinal fluid-based biomarkers and the apolipoprotein E (APOE ε4) genotype.
More recently, attention has turned to non-invasive ophthalmological biomarkers as a possible means of identifying cognitive impairment and Alzheimer's disease(AD). According to the researchers of this paper, Kim et al., previous studies had identified "peripapillary retinal nerve fibre layer (RNFL) thinning in patients with AD."1
These included studies by the UK Biobank, which suggested that "thinner RNFLs could indicate baseline cognitive dysfunction and future cognitive decline over time, leading to an increased risk of AD development."1
However, these studies had primarily focused on population groups with existing diagnoses of AD or mild cognitive impairment (MCI). There was little investigation into whether optical coherence tomography (OCT) assessment could prove a convenient, non-invasive method of cognitive function assessment in a healthy ageing population.
The Research Question
The researchers set out to determine if it was possible to establish a correlation between retinal layer thickness and the development of cognitive impairment and future cognitive decline in a community-based population cohort.
Method
The study – a population-based longitudinal cohort trial - was conducted in Korea and included four hundred and thirty participants. The mean age of the participants was 76.3 years [with an SD of 6.6 years] and 48% were female.
Baseline testing was conducted between September 2010 to September 2011, and a follow-up assessment from September 2015 to September 2016.
The participants underwent a comprehensive ophthalmic exam which included spectral-domain OCT (SD-OCT), intraocular pressure, auto kerato-refractometry, and optical biometry axial length calculation. Spectral-domain optical coherence tomography was used to assess “..the thickness of 6 retinal layers in the macular region, the peripapillary retinal nerve fibre layers (RNFLs), and the subfoveal choroid at baseline."1
The participant's cognitive status was determined by a neuropsychological assessment which included the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K) and the Mini-Mental State Examination (MMSE).
The participants were divided into groups of cognitively normal and cognitively impaired (MCI or dementia).
Findings
Of the original 430 participants, 215 completed the follow-up assessment
The researchers found inter alia, that a thinner baseline total macular RNFL thickness was associated with a more significant decline in the CERAD and MMSE scores.
Furthermore, participants with baseline total macular RNFL thickness below the lowest quartile cut-off value presented a "more significant decline in cognitive scores and a higher prevalence of cognitive impairment and Alzheimer's disease than those with RNFL thickness above the lowest quartile cutoff value."1
Conclusion
The researchers concluded that "....OCT-measured baseline macular RNFL thickness was associated with future cognitive decline." 1
Specifically, a thinner RNFL thickness appeared to predict future cognitive decline. The measurement of RNFL thickness could therefore prove to be a useful non-invasive biomarker for assessing changes in cognitive function. However, further investigations with similar long-term follow-ups were necessary to confirm these findings.
Access the original research here
Kim HM, Han JW, Park YJ, Bae JB, Woo SJ, Kim KW. Association Between Retinal Layer Thickness and Cognitive Decline in Older Adults. JAMA Ophthalmol. Published online May 26, 2022. doi:10.1001/jamaophthalmol.2022.1563
Kim HM, Han JW, Park YJ, Bae JB, Woo SJ, Kim KW. Association Between Retinal Layer Thickness and Cognitive Decline in Older Adults. JAMA Ophthalmol. Published online May 26, 2022. doi:10.1001/jamaophthalmol.2022.1563
References:
1. Kim HM, Han JW, Park YJ, Bae JB, Woo SJ, Kim KW. Association Between Retinal Layer Thickness and Cognitive Decline in Older Adults. JAMA Ophthalmol. Published online May 26, 2022. doi:10.1001/jamaophthalmol.2022.1563
Contributor: Linda Ravenhill
Linda Ravenhill is a medical professional with an MA in Journalism. She has worked in the medical, technology and digital development spaces for over 25 years, & has a particular interest in the impact of technology on the delivery of healthcare in the Sub-Saharan Africa region.
Linda Ravenhill is a medical professional with an MA in Journalism. She has worked in the medical, technology and digital development spaces for over 25 years, & has a particular interest in the impact of technology on the delivery of healthcare in the Sub-Saharan Africa region.
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